Device for detecting a bad road from a moving vehicle

ABSTRACT

A device for detecting a bad or bumpy road from a moving vehicle includes a plurality of wheel speed detectors for detecting the corresponding wheel speeds of a plurality of different wheels, an arithmetic circuit for calculating a difference between values detected in the individual wheel speed detectors, a filter, receiving outputs from the arithmetic circuit, for processing only components in a predetermined frequency band, and a determination circuit for determining if a vehicle is travelling on a bad road based on outputs from the filter. The device easily detects a bad road from a moving vehicle on the basis of outputs from said wheel speed detectors, without being affected by instantaneous variations in the wheel speeds.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for detecting a bad road froma moving vehicle.

2. Description of the Prior Art

In such a conventional device for detecting a bad or bumpy road from amoving vehicle, an ultrasonic wave is emitted from an ultrasonic wavetransmitter mounted on the vehicle, and a reflected wave from the roadsurface is received by a receiver in order to decide whether or not thevehicle is travelling on a bad road.

Often a conventional device for detecting a bad road, as describedabove, may be employed with a suspension control system in an effort toenable a comfortable drive on a bad road. In addition, two examples oftraction control systems found in U.S. Pat. Nos. 4,432,430 and 4,589,511may employ such bad road detector.

With the above conventional device, however, a special circuit isrequired to detect the bad road, thus resulting in an increased cost.

SUMMARY OF THE INVENTION

The present invention has been accomplished to overcome disadvantages ofthe conventional device and it is an object of the present invention toprovide a device for detecting a bad road from a moving vehicle whereinthe travelling of the vehicle on a bad road can be relatively easilydetected on the basis of outputs from wheel speed detectors withoutbeing affected by instantaneous variation in such outputs, without aspecial ultrasonic transmitter and receiver.

To attain the above object, according to the present invention, a deviceis provided for detecting a bad road from a moving vehicle, comprising aplurality of wheel speed detectors for detecting the corresponding wheelspeeds of a plurality of different wheels, an arithmetic circuit forcalculating a difference between values detected in the individual wheelspeed detectors, a filter, receiving outputs from the arithmeticcircuit, for passing components in a predetermined frequency band, and adetermination circuit for determining that the vehicle is travelling ona bad road on the basis of outputs from the filter.

Because it is known that the variation in wheel speeds is associatedwith a predetermined frequency when the vehicle is travelling on a badroad, the instant invention makes it possible to determine whether ornot the vehicle is travelling on a bad road on the basis of thedifference between the wheel speeds. Moreover, since only the variedcomponents in the predetermined frequency band are passed by the filter,variations due to the yaw movement of the vehicle, or the like, can beeliminated to correctly detect a bad road.

In addition, in the above construction, if the determining circuitcomprises an averaging circuit for calculating an average value ofoutputs from the filter in a predetermined time period, and a comparatorwhich produces a signal indicative of decision of the bad road, when anoutput from the averaging circuit has exceeded a predetermined value, itis possible to detect the presence of a bad or irregular road from themoving vehicle independent of instantaneous variations in wheel speed.

Further, in the above construction, if the determining circuit includesa sensitivity adjuster for adjusting the detecting sensitivity of thecircuit to weaken it when the vehicle speed increases, it is possible tooptimize the prevention of accidental or unintended detection of thepresence of a bad road from the moving vehicle when compared with thecase where the detecting sensitivity is constant.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become apparent from reading the following description of thepreferred embodiments, taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a block diagram of a first embodiment of the instantinvention, which is employed in a vehicle equipped with a six-cylinderengine;

FIG. 2 is a graph illustrating the set number of revolutions of theengine;

FIGS. 3 and 4 are flow charts each illustrating a controlling procedureduring the movement of the vehicle; and

FIG. 5 is a block diagram illustrating a second embodiment of theinstant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention when employed in a vehicle equippedwith a six-cylinder engine will now be described with reference to theaccompanying drawings.

FIGS. 1 to 4 illustrate a first embodiment. Referring first to FIG. 1,the speeds Wlf and Wrf of left and right driving wheels in a vehicle,e.g., left and right front wheels in a front wheel drive vehicle, aredetected by a left front wheel speed detector Slf and a right frontwheel speed detector Srf, respectively. The speeds Wlr and Wrr of leftand right trailing wheels, e.g., left and right rear wheels, are alsodetected by a left rear wheel speed detector Slr and a right rear wheelspeed detector Srr, respectively.

The left and right front wheel speeds Wlf and Wrf, detected by the leftand right front wheel speed detectors Slf and Srf, are delivered to achange-over selecting circuit 1 which is changed over between ahigh-selection mode which selects a higher one of the left and rightwheel speeds Wlf and Wrf as a front wheel speed Wf, and a low-selectionmode which selects a lower one of the left and right wheels speeds Wlfand Wrf as a front wheel speed Wf, depending upon the vehicle speed. Ifthe vehicle speed is at an extremely low level, for example, lower than4 km/hr, the change-over selecting circuit 1 changes to thelow-selection mode.

On the other hand, the left and right rear wheel speeds Wlr and Wrrdetected by the left and right rear wheel speed detectors Slr and Srrare input to a selecting circuit 2 which is operated in response to theselecting operation of the selecting circuit 1. Thus, the speed of therear wheel on the same side as selected by the changeover selectingcircuit 1 is selected by the selecting circuit 2. For example, when theleft front wheel speed Wlf is selected as the front wheel speed Wf inthe change-over selecting circuit 1, the left rear wheel speed Wlr isselected as the rear wheel speed Wr in the selecting circuit 2. This isfor the purpose of eliminating a difference in length between left andright travel paths in a turn.

Values detected by the left and right rear wheel speed detectors Slr andSrr are also applied to a vehicle speed arithmetic circuit 3 where thevehicle speed is calculated according to the following equation:##EQU1## That is, an average value between the left and right rear wheelspeeds Wlr and Wrr is delivered as a vehicle speed V from the vehiclespeed arithmetic circuit 3, and such an output signal is supplied to aninverted input terminal of a comparator 4. A reference signalcorresponding to an extremely slow speed value Vm, e.g., 4 km/hr, issupplied from a reference terminal 5 to a non-inverted input terminal ofthe comparator 4, and if the vehicle speed V is for example, at anextremely low speed lower than 4 km/hr, then a high level signal isproduced from the comparator 4 and supplied to the change-over selectingcircuit 1. Therefore, when the output from the comparator 4 assumes thehigh level, the change-over selecting circuit 1 changes to thelow-selection mode.

The front wheel speed Wf selected in the change-over selecting circuit 1and the rear wheel speed Wr selected in the selecting circuit 2 areapplied to a slip rate arithmetic circuit 6 where the slip rate λ iscalculated according to the following equation: ##EQU2##

The slip rate λ calculated in the slip rate arithmetic circuit 6 isapplied to a differentiating circuit 7 where a differential value λ(where λ=dλ/dλ) of the slip rate λ is calculated.

For a characteristic value indicative of the slipped state of either theleft or right driving wheel, i.e., front wheel, reference valuesrespectively corresponding to the slip rate λ and the differential sliprate λ are set in a reference value determination circuit 8 in the formof a function of the rear wheel speed Wr representative of the vehiclespeed. Moreover, a set of these references values are prepared for eachroad condition of a different coefficient of friction, for example, aflat road and a bumpy road (bad road).

More specifically, for the reference values corresponding to the sliprate λ, F₁ (Wr)=k₁ Wr+C₁ and F₂ (Wr)=k₂ Wr+C₂ are prepared for each ofthe road conditions. In addition, for the reference values correspondingto the differential slip rate λ, f₁ (Wr)=r₁ Wr+D₁ and f₂ (Wr)=r₂ Wr+D₂are prepared in correspondence to each road condition, wherein k₁, k₂,C₁, C₂, r₁, r₂, D₁ and D₂ are constants for determining the referencevalues F₁ (Wr), F₂ (Wr), f₁ (Wr) and f₂ (Wr) and prepared for eachdifferent road condition. These constants (generated in constantreference value change-over means 9) and the rear wheel speed Wrselected in the selecting circuit 2 are applied to the reference valuedetermination circuit 8.

It should be noted that the reference values F₁ (Wr) and f₁ (Wr), havingthe subscript 1, are set for a preliminary control and at levels smallerthan the reference values F₂ (Wr) and f₂ (Wr), having the subscript 2,and moreover all the references for bumpy (bad) roads are set at largerlevels than the corresponding reference values for a flat road.

The values detected in the left and right front wheel speed detectorsSlf and Srf are applied to a subtraction circuit 10 which provides anabsolute value |wlf-Wrf|=|ΔWf| of a difference between both the frontwheel speeds Wlf and Wrf. The substraction circuit 10 is connected to anon-inverted input terminal of a comparator 11. A signal correspondingto a reference wheel speed difference ΔW_(o) is input from a referenceterminal 16 to an inverted input terminal of the comparator 11. Thispermits the comparator 11 to generate a high level signal when theabsolute value |ΔWf| of the difference between front wheel speedsexceeds the reference wheel speed difference ΔW_(o). In other words,when it is decided that one of the front wheels is excessively slippingand racing, the comparator 11 produces the high level signal.

The differential slip rate λ calculated in the differentiating circuit 7is applied to non-inverted input terminals of comparators 12 and 13. Thereference value f₂ (Wr) corresponding to the differential slip rate λ issupplied from the reference value determination circuit 8 to an invertedinput terminal of the comparator 12, while the reference value f₁ (Wr)is supplied to an inverted input terminal of the comparator 13. On theother hand, the front wheel speed Wf selected in the change-overselecting circuit 1 is input to non-inverted input terminals ofcomparators 14 and 15. Further, the reference value F₁ (Wr)corresponding to the slip rate λ is fed from the reference valuedetermination circuit 8 to an inverted input terminal of the comparator14, while the reference value F₂ (Wr) is fed to an inverted inputterminal of the comparator 15.

The comparator 12 decides whether or not the differential slip rate λ istoo large. The comparator 15 decides or not the slip rate λ is toolarge. The comparators 13 and 14 also decide whether or not thedifferential slip rate λ and the slip rate λ are too large. If thesevalues are too large, then the comparators 13 and 14 produce high leveloutputs.

An output from the comparator 11 is applied to an input terminal of ANDgate 17, while an output from the comparator 4 is applied to the otherinput terminal of the AND gate 17. More specifically, when the vehiclespeed is extremely low and one of the front wheels is racing orspinning, the output from the AND gate 17 assumes a high level. The ANDgate 17 is connected to OR gate 18.

In addition to the AND gate 17, outputs from the comparator 12, an ANDgate 19 and the comparator 15 are applied to the OR gate 18. Outputsfrom the comparators 13 and 14 are applied to two input terminals of ANDgate 19. Thus, an output from the OR gate 18 assumes a high level, whenat least any one of the following cases is established: when the outputfrom the AND gate 17 assumes a high level, that is, the vehicle speed isextremely low and one of the front wheels is racing; when thedifferential slip rate λ is too large; when the slip rate λ is toolarge; and when the output from AND gate 19 assumes a high level, thatis, it is decided for preliminary control purposes that the wheel isabout to begin slipping excessively.

The OR gate 18 is connected to one of the input terminals of an OR gate26. The output terminals of the comparators 13 and 14 are connectedrespectively to input terminals of an OR gate 20 which is connected toone of the input terminals of an AND gate 25. Further, the output fromthe comparator 4 is input to the other input terminal of AND gate 25.Thus, an output from the AND gate 25 assumes a high level when thevehicle speed is extremely low and either the slip rate λ or thedifferential slip rate λ meets a deciding condition for deciding thatthe wheel is about to begin slipping excessively. The output of AND gate25 is connected to one of the input terminals of AND gate 24.

An output of a comparator 22 is input to the other input terminal of ANDgate 24, and an inverted input terminal of the comparator 22 isconnected to an output terminal of an engine revolution-number settingcircuit 21. The number of revolutions of engine relative to the rearwheel speed Wr, representative of the vehicle speed, is set in theengine revolution-number setting circuit 21, as shown in FIG. 2, and therear wheel speed Wr selected in the selecting circuit 2 is applied tothe engine revolution-number setting circuit 21. That is, the enginerevolution-number setting circuit 21 produces a signal indicative of theset number N_(FC) of revolutions of engine in accordance with the rearwheel speed Wr input thereto and applies it to the inverted inputterminal of the comparator 22. Further, the value detected by enginerevolution-number detector Sn is applied to a non-inverted inputterminal of the comparator 22. Thus, the comparator 22 feeds a highlevel signal into AND gate 24 when the actual number Ne of revolutionsof engine detected in the engine revolution-number detector Sn hasexceeded the number N_(FC) of revolutions of engine set in the enginerevolution-number setting circuit 21. That is, the AND gate 24 producesa high level signal, as the number of revolutions of engine exceeds aset value when the vehicle speed is at an extremely low level and thefront wheel is about to begin to slip excessively.

The output from AND gate 24 is applied to the other input terminal ofthe OR gate 26. The output from the OR gate 18 has been applied to theone input terminal of OR gate 26, as described above, and therefore, anoutput from the OR gate 26 assumes a high level, in response to theestablishment of at least one of the following cases: when the drivingor front wheel has slipped excessively; when the driving wheel is aboutto excessively slip; and when the number of revolutions of engine hasexceeded the set value when the vehicle speed is extremely low and thedriving wheel is about to slip excessively.

The output from the OR gate 26 is input to an engine output controller27 which deactivates the combustion stroke of an engine to control thedriving force, thereby preventing an excessive slippage of the drivingwheel. When the output from the OR gate 26 has assumed the high level,the engine output controller 27 deactivates the combustion stroke of theengine. Moreover, the engine output controller 27 deactivates thecombustion strokes of cylinders of the number set in a cylinder-numberdetermination circuit 28 concurrently with a change of constants k1, k2,C1 and C2 output from the reference value change-over means 9 inresponse to detection, by a bad road detecting device 29, of thesituation that the vehicle is travelling on a bad road. That is, whenthe vehicle is travelling on the bad road, excessive slippage isacceptable to some extent, and supplying of fuel to the cylinders of thenumber selected according to the rear wheel speed Wr, representative ofthe vehicle speed, is cut off by means of the engine output controller27.

The rear wheel speed Wr is fed from the selecting circuit 2 to thecylinder-number determination circuit 28. The numerals indicative of thenumbers of cylinders are set in the cylinder-number determinationcircuit 28, for example, the number 3 when the rear wheel speed Wr isless than a set value α, e.g., 12 km/hr (Wr<α), for example, the numeral4 when the rear wheel speed Wr is more than the set value α and lessthan a set value β, e.g., 20 km/hr (α≦Wr<β), and for example, the number6 when the rear wheel speed Wr is more than the set value (β≦Wr). Asignal corresponding to each of the numbers of cylinders is applied tothe engine output controller 27. That is, as the vehicle speedrepresented by the rear wheel speed Wr is reduced, the number ofcylinders whose combustion stroke is deactivated is reduced.

The bad road detecting device 29 comprises rear wheel speed detectorsSlr and Srr, an arithmetic circuit 30, a filter 31, a determinationcircuit 36 and a high selection circuit 35. The rear wheel speeddetectors Slr and Srr are connected to the arithmetic circuit 30 and thehigh selection circuit 35, respectively. A difference ΔWr (Wlr-Wrr)between both rear wheel speeds is calculated in the arithmetic circuit30, while the higher of both rear wheel speeds Wlr and Wrr is selectedas one representative of the vehicle speed in the high selection circuit35. The determination circuit 36 comprises an averaging circuit 32, acomparator 33 and a sensitivity adjuster 34.

The filter 31 is of a recursive type which passes only those componentsof varied values of the difference ΔWr which are in a given frequencyband about predetermined resonance frequencies, e.g., 10 to 15 Hz of avehicle suspension in a moving direction of the vehicle or in a verticaldirection, and in the filter 31, a calculation is made according to thefollowing equation:

    Y.sub.n =A.sub.1 ·Y.sub.n-1 +A.sub.2 ·Y.sub.n-2 +A.sub.3 ·Y.sub.n-3 . . . +B.sub.1 ·X.sub.n +B.sub.2 ·X.sub.n-1 +B.sub.3 ·X.sub.n-2          (3)

wherein A₁, A₂, A₃ . . . B₁, B₂, B₃ . . . are constants thedetermination of which forms the band-pass filter: Y_(n), Y_(n-1), . . .are values output from the filter 31; and X_(n), X_(n-1), . . . arefeedback values, with the subscripts n, n-1, n-2, . . . representing apresent value, the previous value, the next previous value, and so on.

A time-average value of the outputs from the filter 31 is calculated inthe averaging circuit 32 (wherein the "time-average value" indicates avalue obtained by averaging the outputs within a predetermined time),and an output Y from the averaging circuit 32 is applied to anoninverted input terminal of the comparator 33. On the other hand, therear wheel speed Wlr or Wrr selected in the high selection circuit 35 isapplied to the sensitivity adjuster 34 as a speed representative of thevehicle speed. Moreover, an output value or reference value G is set inthe sensitivity adjuster 34 to increase as the vehicle speed increases,and a signal corresponding to the reference value G output from thesensitivity adjuster 34 is applied to an inverted input terminal of thecomparator 33. Thus, when the time-average value of the differencevalues between the rear wheel speeds in the given frequency band hasexceeded the reference value G, the comparator 33 supplies a high levelsignal to the engine power controller 27 on the basis of a decision thatthe vehicle is traveling on a bad road. Moreover, the detectingsensitivity thereof is reduced as the vehicle speed is increased.

When the vehicle is travelling on a bad road, the bad road detectingdevice 29 enables the condition that the vehicle is travelling on a badroad to be easily and correctly detected on the basis of the fact thatthe variation in wheel speed is associated with the resonance frequencyof the vehicle suspension. Because of the decision from the time-averagevalue, the condition that the vehicle is travelling on a bad road can bedetected independent of instantaneous variations.

The operation of this embodiment will be described below. Referring toFIG. 3 illustrating a control procedure, the individual wheel speedsWlf, Wrf, Wlr, and Wrr are read in a first step S1, and the trailingwheel speeds Wlr and Wrr are averaged to provide a vehicle speed V insecond step S2. Then, it is decided in a third step S3 whether or notthe vehicle speed V is lower than the set value Vm, i.e., whether or notthe vehicle speed V is at an extremely low level. When it is decided inthe third step S3 that the vehicle speed V is at the extremely lowlevel, a flag F_(L) becomes "1" in a fourth step S4, progressing to afifth step S5.

In the fifth step S5, it is decided whether or not the absolute value|ΔWf|, or a difference between the driving wheel speeds, exceeds the setvalue ΔW_(o). That is, it is decided whether or not either one of thefront wheels is racing, and when it is decided that such one wheel isnot racing, i.e.,|ΔWf|≦ΔW_(o), progress is made to an eighth step S8.Also, when the vehicle speed V is decided not to be at the extremely lowlevel at the third step S3, the flag F_(L) becomes "0" in a seventh stepS7, progressing to the eighth step S8. Further, when it is decided atthe fifth step S5 that the one driving wheel is racing, progress is madeto a 29th step S29.

At the eighth step S8, it is decided whether or not the right frontwheel speed Wrf is larger than the left front wheel speed Wlf. That is,the magnitudes of the both front wheel speeds are compared at the eighthstep S8, because one of the front wheel speeds is selected as a frontwheel speed in the change-over selecting circuit 1 depending upon eitherthe high selection mode or the low selection mode. When Wrf>Wlf isdecided in the eighth step S8, a flag F_(F) becomes "0" at the ninthstep S9, followed by an 11th step S11. When Wrf>Wlf is decided in theeighth step S8, the flag F_(F) is changed to "1" at a 10th step S10,followed by the 11th step S11.

In the 11th step S11, it is decided whether or not the vehicle speed isextremely low, i.e., F_(L) =1. When F_(L) =1, i.e., when the vehiclespeed is extremely low, it is decided in a 12th step S12 whether or notthe right front wheel speed Wrf is larger than the left front wheelspeed Wlf, i.e., whether or not F_(F) is "1". When F_(F) =1, Wf=Wlf isestablished in a 13th step S13 and then, Wr=Wlr is established in a 14thstep S14, progressing to a 22nd step S22. On the other hand, when F_(F)=0 at the 12th step S12, Wf=Wrf is established in the 15th step S15 andthe, Wr=Wrr at 16th step S16, progressing to the 22nd step S22.

When F_(L) =0 in the 11th step S11, i.e., when the vehicle speed is notat the extremely low level, it is judged in a 17th step S17 whether ornot F_(F) is "1". When F_(F) =1, a step is taken from the 17th step S17successively to 18th and 19th steps S18 and S19 where Wf=Wrf and Wr=Wrrare established, proceeding to the 22nd step S22. Alternatively, whenF_(F) =0 at the 17th step S17, a step is taken to 20th step and 21ststep S20 and S21 in succession, where Wf=Wlf and Wr=Wlr are established,proceeding to the 22nd step S22.

In the 22nd step S22, the slip rate λ is calculated and then, in a 23rdstep S23, the differential slip rate λ is calculated. At a 24th stepS24, it is judged whether or not the vehicle speed is extremely low,i.e., whether or not F_(L) =1. When F_(L) =1, i.e., when the vehiclespeed is extremely low, a step is taken to a 25th step S25, whereas whenF.sub. =0, i.e., when the vehicle speed is not extremely low, a step istaken to a 30th step S30. In the 25th step S25, it is judged whether ornot Wf>F₁ (Wr). When Wf>F₁ (Wr), a step is taken to a 27th step S27,whereas when Wf≦F₁ (Wr), a step is taken to a 26th step S26. In stepS26, it is decided whether or not λ>f₁ (Wr). When λ>f₁ (Wr), a step istaken to a 27th step S27, on the one hand, and when λ≦f₁ (Wr), a step istaken to a 34th step S34, on the other hand. In step S27, the set numberN_(FC) of revolutions of engine according to the rear wheel speed Wr issearched from a table shown in FIG. 2, and in step S28, the searched setnumber N_(FC) of revolutions of engine is compared with the actualnumber Ne of revolutions of engine. If Ne>N_(FC), a step is taken to a29th step S29, while if Ne≦N_(FC), a step is taken to the 30th step S30.

At the 30th step S30, the aforesaid differential slip rate λ is comparedwith the reference value f₂ (Wr); and if λ>f₂ (Wr), a step is taken tothe 29th step S29. On the other hand, if λ≦f₂ (Wr), a step is taken to a31st step S31. In the step S31, it is decided whether or not Wf>F₁ (Wr).If Wf>F₁ (Wr), a step is taken to a 32nd step S32, whereas if Wf≦F₁(Wr), a step is taken to a 34th step S34. In step S32, it is decidedwhether or not λ>f₁ (Wr). If yes, a step is taken to the 29th step S29,whereas if λ≦f₁ (Wr), a step is taken to a 33rd step S33. In step S33,it is decided whether or not Wf>F₂ (Wr). If Wf>F₂ (Wr), a step is takento the 29th step S29, whereas if Wf≦F₂ (Wr), a step is taken to the 34thstep S34. In the 29th step and 34th steps S29 and S34, a flag F_(S) isset at "1" and "0", respectively. If the flag F_(S) is set at "1" in thestep S29, a step is taken to a 35th step S35.

When steps S25 and S26 are yes, this means that the vehicle istravelling at an extremely low speed and is about to slip excessively.In addition, the flag F_(S) represents the condition when the vehicle isslipping excessively or is about to slip excessively. That is, F_(S) =1indicates that the vehicle is slipping excessively or is about to slipexcessively and hence, the fuel is cut to the engine, as describedbelow.

The 35th step S35 and succeeding steps indicate a procedure for thedetection of the bad road by detecting device 29. At the 35th step S35,the difference Wr between the both rear wheel speeds Wlr and Wrr iscalculated, and at the 36th step S36, the filtering is carried out. Theabove-described components of the difference ΔWr picked by the filteringare time-averaged at the 37th step S37, and the resulting time-averagevalue Y is judged in the 38th step S38 whether or not it is smaller thanthe reference value G. When Y≦G in the 38th step 38, i.e., when thevehicle is not travelling on a bad road, a flag F_(D) is set at "0". Onthe other hand, when Y>G, i.e., when it is decided that the vehicle istravelling on a bad road, the flag F_(D) is set at "1".

After completion of the procedures for deciding whether or not thevehicle is slipping excessively or is about to slip excessively, i.e.,whether or not the flag F_(S) is at "1" and whether or not the vehicleis travelling on the bad road, i.e., the flag F_(D) is at "1", asdescribed above, the controlling of the engine power is carried outaccording to a procedure illustrated in FIG. 4.

Referring to FIG. 4, it is decided in a first step L1 whether or not theflag F_(S) is "1", i.e., whether the vehicle is slipping excessively oris about to slip excessively. If F_(S) =0, a step is taken to a secondstep L2 where a flag F_(C) is set at "0". This flag F_(C) representswhether or not the fuel cut step for controlling the number of cylindershas been performed in the immediately proceeding control cycle, andF_(C) =1 indicates that the fuel cut step for controlling of the numberof cylinders has been performed. At the next third step L3, the fuel cutcommand is released, resulting in a normal operation of engine.

When F_(S) =1 in the first step L1, a step is taken to a fourth step L4where it is decided whether or not the vehicle is travelling on a badroad, i.e., whether or not F_(D) =1. If F_(D) =0 is established in afifth step L5, and then, the supply of fuel is cut off in a sixth stepL6. More specifically, when the vehicle is slipping excessively or isabout to slip excessively during travelling on a road which is not a badroad, controlling of the number of cylinders is not conducted, and thecombustion stroke of each of the cylinders is inoperative untilexcessive slipping no longer occurs.

When F_(D) =1 in the fourth step L4, a step is taken to a seventh stepL7 where it is decided whether or not the rear wheel speed Wr,repesentative of the vehicle speed, is lower than α, e.g., 12 km/hr.When Wr>α, N=1 is established in an eighth step L8 and then, it isjudged in a ninth step L9 whether or not F_(C) =0. When F_(C) =0, acount value C_(C) is set at N in a 10th step, L10, proceeding to a 14thstep L14. When F_(C) =1, the 10th step L10 is skipped proceeding to the14th step L14.

When Wr≧a in the seventh step L7, it is decided in an 11th step L11whether or not Wr>β (e.g., 20 km/hr). When α≦Wr>β, N=2 is established ina 12th step L12 and then, it is judged in a 13th step L13 whether or notF_(C) =0. When F_(C) =0, a step is taken to the 10th step L10. WhenF_(C) =1, a step is taken to the 14th step L14. Alternatively, whenWr≧β, a step is taken from the 11th step L11 to the fifth step L5.

At the 14th step L14, it is judged whether or not the count value C_(C)is "0". When C_(C) =1, a fuel cut command is effected in a 15th stepL15; F_(C) =1 is established in a 16th step L16 and C_(C) =C_(C) -1 isestablished in a 17th step L17. Alternatively, when C_(C) =0 in the 14thstep L14. F_(C) =0 is established in an 18th step 18 and then, the fuelcut command is released at a 19th step L19.

The controlling procedure will be summarized as follows: As the vehicleis slipping excessively or is about to slip excessively, fuel cutcontrol for all cylinders is carried out when the vehicle is travellingon a road which is not bad, or when Wr≧β even if the vehicle istravelling on a bad road. Alternatively, when the vehicle is travellingon a bad road and Wr<α, the supply of fuel is cut for every othercylinder, i.e., fuel cut is effected for three out of six cylinders.Alternatively when the vehicle is travelling on a bad road and α≦Wr<β,adjacent two cylinders are subjected to a fuel cut command, but acylinder next to the two adjacent cylinders is not subjected to the fuelcut, i.e., four out of six cylinders are subject to the fuel cut.

In this manner, when the vehicle is slipping excessively or is about toslip excessively, the fuel cut control for the number of cylinderscorresponding to the vehicle speed, depending upon whether or not thevehicle is travelling on a bad road, is effected, thus resulting in areduction in driving force, which decreases or avoids excessiveslippage. Moreover, in detecting a bad road, a value obtained byaveraging the values of the difference between the railing wheel speedswithin a predetermined time is compared with the reference value G,wherein the difference between the trailing wheel speeds increases asthe vehicle speed increases. Therefore, if the reference value G isconstant, the travelling of the vehicle is liable to be unintendedly oraccidentally detected to be on a bad road, as the vehicle speedincreases. However, the arrangement in this embodiment is such that thereference value G increases as the vehicle speed increases and hence, itis possible to optimize the prevention of accidental or unintendeddetection of a bad road.

The above embodiment illustrates the bad road detecting device 29 whichcomprises the high selection circuit 35 for selecting the higher one ofthe left and right rear wheel speeds Wlr and Wrr as a vehicle speed, anda sensitivity adjuster 34 to which is applied the vehicle speed selectedin circuit 35 and which increases the reference value G as the vehiclespeed increases. With this device 29, a signal corresponding to thevariable reference value G delivered from the sensitivity adjustor 34 isapplied to the inverted input terminal of the comparator 33.Alternatively, the high selection circuit 35 and the sensitivityadjuster 34 may be eliminated from the bad road detecting 29, so thatonly a signal corresponding to a fixed reference value G may be appliedto the inverted input terminal.

FIG. 5 illustrates a second embodiment of the present invention havingsuch an arrangement. In the second embodiment, when the time-averagevalue of the differences ΔWr between the rear wheel speeds in a givenfrequency band exceeds a fixed reference value G, the comparator 33applies a high level signal to the engine output controller 27 on thebasis of the decision that the vehicle is travelling on a bad road.

More specifically, a determination circuit 36' in a bad road detectingdevice 29' in the embodiment shown in FIG. 5 includes a referenceterminal 34' which produces a signal corresponding to the fixedreference value G. This signal is applied to the inverted input terminalof the comparator 33 and compared with an output Y received in thenoninverted input terminal of the comparator 33 from the averagingcircuit 32.

Unlike the first embodiment, front wheel speed detectors Slf and Srf areconnected to the arithmetic circuit 30 of the bad road detecting device29' in the second embodiment. Therefore, in the arithmetic circuit 30, adifference ΔWf (Wlf-Wrf) between the both front wheel speeds iscalculated. For this reason, in the controlling procedure, the 35th stepS35 in the first embodiment illustrated in FIG. 3 is changed to a stepof "calculating ΔWf" in the second embodiment. Other steps are similarto those in the first embodiment.

Although the fuel cut has been conducted by means of the engine outputcontroller 27 to control the driving force in the above two embodiments,it should be understood that an intake throttle valve control devicedriven, for example, by a pulse motor may be operated to bring an intakethrottle valve to a closed position; either the timing of ignition by aspark ignitor of an engine may be angularly delayed or such ignition maybe cut off, or the supercharging pressure may be reduced by a device forcontrolling the supercharging pressure of an intake air supplied to anengine.

Although a specific form of embodiment of the instant invention has beendescribed above and illustrated in the accompanying drawings in order tobe more clearly understood, the above description is made by way ofexample and not as a limitation to the scope of the instant invention.It is contemplated that various modifications apparent to one ofordinary skill in the art could be made without departing from the scopeof the invention which is to be determined by the following claims.

We claim:
 1. A device for detecting irregular road from a movingvehicle, comprising:a plurality of wheel speed detectors for detectingcorresponding wheel speeds of a plurality of wheels of the vehicle; anarithmetic circuit for calculating the difference between wheel speedsdetected by the individual wheel speed detectors; a filter receiving anoutput from said arithmetic circuit and passing components in apredetermined frequency band to an output; and a determination circuitmeans, receiving said filter output, for determining if the vehicle istravelling on a bad or bumpy road, in response to the filter output, andoutputting a signal indicative thereof.
 2. The device of claim 1,wherein said predetermined frequency band is set to a band generallycorresponding to the resonant frequencies of the vehicle suspensionoccurring in a vehicle-advancing direction and in a vertical direction.3. The device of one of claims 1 or 2, wherein said wheel speeddetectors include detectors for detecting the wheel speeds of the leftand right trailing wheels of the vehicle, and inputting said left andright trailing wheel speeds to said arithmetic circuit.
 4. The device ofone of claims 1 or 2, wherein said wheel speed detectors includedetectors for detecting the wheel speeds of the left and right drivingwheels, and inputting said left and right driving wheel speeds to saidarithmetic circuit.
 5. The device of one of claims 1 or 2, wherein saiddetermination circuit means includes an averaging means for calculatinga time-average of the outputs from said filter, and a comparing means,receiving an output from said averaging means, for outputting saidirregular road signal when said output of said averaging means exceeds apredetermined value.
 6. The device of claim 5, wherein saiddetermination circuit means further includes a sensitivity adjustermeans for adjusting a determination sensitivity of said determinationcircuit means and reducing the determination sensitivity in response toan increase in a vehicle speed, and wherein the output of saidsensitivity adjuster means is said predetermined value of said comparingmeans.
 7. The device of claim 6, further comprising a selecting circuit,receiving inputs from left and right trailing wheel speed detectors, foroutputting the higher of the two wheel speeds to said sensitivityadjuster means.
 8. A device for detecting an irregular road from amoving vehicle, comprising:a wheel speed detector for detecting a wheelspeed of the vehicle, an arithematic circuit for eliminating from theoutput of the wheel speed detector an amount corresponding to a vehiclespeed; a filter receiving an output from said arithmetic circuit andpassing components in a predetermined frequency band to an output; and adetermination circuit means, receiving said filter output, fordetermining if the vehicle is travelling on an irregular road, inresponse to the filter output, and outputting a signal indicativethereof.
 9. A device for detecting an irregular road from a movingvehicle, comprising:wheel speed detector for detecting a wheel speed ofthe vehicle; a wheel speed variation detecting means for detecting avariation in the level of an output from the wheel speed detector; areference value generating means for generating a reference valuevariable in response to a vehicle speed; and a detecting means fordetecting a road surface to be irregular when the output from the wheelspeed variation detecting means is greater than the reference value fedfrom the reference value generating means.